Josko Bobanovic

Barotropic Circulation Variability on Canadian Atlantic Shelves

Thesis Approved April 1997

Barotropic variability of the Canadian Atlantic Shelf on synoptic
time-scales is examined using data analysis, statistical and dynamical
models. The main objective is to understand the connections between
the subregions and develop models that can be used operationally.
Data are used to determine dominant scales, run statistical models and
validate dynamical models. Data assimilation is used to infer open
boundary conditions for the dynamical models. In the first study
synoptic variability of the Labrador Shelf is examined using a limited
area model. Wind and upstream boundary forcing are found to be the
most important sources of the variability. Based on model results a
forecasting scheme is designed and tested. The second subregional
study concentrated on the variability in the Gulf of Saint
Lawrence. Boundary forcing via Cabot Strait is found to be the
dominant source of variability. Data analysis indicates the presence
of resonances in the Gulf, some of which can be related to wind and
boundary forcing. In the last study, a large scale model of the
Canadian Atlantic Shelf forced by wind and air pressure is used to
examine connections between the regions. The model showed very good
predictive skill for sea level and along-shore coastal currents. The
wind driven flow from the Newfoundland Shelf is the most dominant
source of remote variability for the Gulf of Saint Lawrence and the
Scotian Shelf. High frequency signals from the Newfoundland Shelf can
cross the Laurentian Channel and directly force the Scotian Shelf.
Non-isostatic pressure forcing within the domain is negligible. The
model driven by forecast winds can be run operationally to predict sea
level and currents variability or supply boundary conditions for more
sophisticated limited area model.